• Contractors report that design mixes are frequently adapted to individual jobs. Pouring a whole job on the same day helps ensure consistent curing.
• The “how-to” part is an important aspect of using a prepared concrete mix. Find out what you’ll be getting and make sure you’ll have the information you need to go with it.
• Melamine makes an excellent mold for pre-casting. Rubber forms work well for molding special details.
• Many contractors vibrate pre-cast molds after pouring to get the air bubbles out. The vibration also helps aggregate to sink to the bottom, which becomes the top when the countertop is de-molded.
• Contractors who pre-cast generally de-mold their countertops within three to five days. They also like to wait 28 days before delivery and installation, though some have worked shorter turn-around times on occasion with no ill results.
• The finish is the wear surface protecting the concrete or engineered cement product from abrasion and staining. A variety of sealers can be used. If you ask around, you’ll find different contractors prefer different products for different reasons. Penetrating sealers give the surface a more natural look. They also allow the surface to develop a patina. Depending on the use and abuse the surface gets, a wax maintenance schedule may be recommended. Topical sealers, such as urethane and epoxy, encapsulate the surface and make it pretty impenetrable, but they have a plastic look and are difficult to repair.
• Although concrete is durable and can take heat, advise your clients to use trivets and cutting boards, and to wipe up spills promptly to avoid staining. Clients should also avoid using citrus-based cleaning products and acidic liquids, such as vinegar and lemon juice, on concrete countertops protected by penetrating sealers.
